Recent posts not appearing in their assigned categories

I’m having a problem with recent posts not appearing in their assigned categories. This has only started happening in the past few days and I have no idea why. So basically any new posts I add to categories are now not appearing when the category is clicked. I have searched the internet for ages to try and find a solution but have had no success. I have also tried deactivating plug ins etc and absolutely nothing has fixed it.

This is doing my head in and I really need to get this fixed so if anyone can help me out it would be much appreciated.